Solenoid device having a non-rotatably mounted coil bobbin



Sept. 20, 1966 R. L. VALLEAU SOLENOID DEVICE HAVING A NON-ROTATABLY MOUNTED COIL BOBBIN Filed Aug. 28, 1964 Inventor Robert Lfllalleau I Ill United States Patent nois Filed Aug. 28, 1964, Ser. No. 392,697 4 Claims. (Cl. 335255) This invention relates to the construction of a solenoid and to a method of fabricating a solenoid.

A common form of solenoid manufactured in large quantities, and over which the present invention is an improvement, has a frame, a coil assembly secured to said frame, and a plunger guide tube within the coil for guiding the reciprocatory movement of the plunger within the coil. The coil assembly includes a central coil wound on a cylindrical tube and a pair of opposed insulating headers disposed at opposite ends of the coil between the coil and the frame. In fabricating this prior art coil assembly, the headers and cylindrical tube for the coil are forced on the plunger tube and this sometimes results in distortion of the plunger tube so that the plunger binds therein.

Another problem with solenoids of the aforementioned construction is the likelihood of the coil to turn or to twist relative to the plunger tube and thereby lose its orientation with respect to the solenoid frame, the coil being oriented and held against turning only by the frictional force between the coil and its supporting plunger tube. Accordingly, an object of the present invention is to construct a solenoid in a novel manner so as to eliminate the forcing of headers for a coil on a plunger tube and the resulting distortion of the plunger tube for the solenoid plunger.

Another object of the invention is to secure the coil of a solenoid in a definite position with respect to the plunger tube by .interlocking the supporting coil structure or bobbin with the frame.

According to a more specific object of the present invention, a coil is wound on a one-piece bobbin having integrally formed header portions thereon and the bobbin fits loosely over the plunger tube, which tube is adapted to be forced on the plunger stop. Under this object of the invention one of the headers is provided with interlocking elements which register with mating elements on the frame to hold the bobbin and coil against twisting relative to the frame.

In accordance with the preferred embodiment of the present invention, the solenoid is constructed by staking a plunger stop to a U-shaped frame member. An integral one-piece bobbin having a coil wound thereon is positioned on a thin-walled plunger tube prior to forcing the plunger tube onto the staked stop for the plunger. The lower header has projections on its outer surface. The projections fit into cor-responding openings in the U-shaped frame member to hold the bobbin and coil against rotation. A top frame element is disposed over the top header and a projecting end of the plunger tube, and the top frame element is clenched to the U-shaped frame member.

Other and further objects of the present invention will be apparent from the following description and claims and are illustrated in the accompanying drawing which, by way of illustration, shows preferred embodiments of the present invention and the principles thereof and what is now considered to be the best mode contemplated for applying these principles. Other embodiments of the invention embodying the same or equivalent principles may be used and structural changes may be made as desired by those skilled in the art without departing from the present invention.

In the drawings:

FIG. 1 is a perspective view of a solenoid constructed in accordance with the preferred embodiment of the invention;

FIG. 2 is an expanded view showing the elements, except the plunger, comprising the solenoid of FIG. 1; and

FIG. 3 is a sectional view taken through the frame, bobbin and metal tubing.

Referring now to the drawing, and more particularly to FIG. 1, there is illustrated a solenoid 10 constructed in accordance with the preferred embodiment of the invention and having a vertically reciprocal plunger 11 movable within the interior of a coil 12 disposed in a frame 13.

When the coil 12 is energized through electrical leads 14, the plunger 11 is pulled into the coil 12 and comes into engagement with a solenoid stop 15 which limits the inward movement of the plunger 11. The solenoid plunger 11 slides easily within the hollow interior of a metal tube or tubing 18, the interior bore 19 of the tube 18 serving to guide the cylindrical plunger 11 during its reciprocal movement. The plunger 11 is closely dimen sioned to the size of the bore 19 of the plunger tube 18 so that distortions of the tube 18 may not cause stopping or frictional interference with the easy sliding of the plunger 11.

As an important aspect of the present invention, the coil 12 is wound on an integral, one-piece bobbin 20 which has a pair of opposed headers or flanges 21 and 22 integrally formed at opposite ends of a center cylindrical member 24. The bobbin 20 has an interior bore 25 which is adapted to have a loose sliding fit with the exterior surface of the plunger tube 18. That is, cylindrical member 24 is not forced under pressure over a plunger tube as was the prior art practice. Hence, an easy sliding fit of the bobbin 20 with plunge-r tube 18 affords no appreciable frictional force preventing turning of the coil relative to the plunger tube 18 as was present with the prior construction.

In lieu of this frictional force, the lower header 21 of the present invention is adapted to be interlocked to a base portion 29 of the frame 13 by integrally formed and downwardly extending projections 30 spaced to fit is spaced receiving openings 32 formed in the base portion 29 of the frame 13. When the solenoid is assembled, as illustrated in FIG. 3, the projections 30 prevent rotation of the bobbin 20 relative to the frame 13 and plunger tube 18 and thereby a positive mechanical lock is achieved in lieu of the frictional locking force employed heretofore.

In fabricating prior art solenoids, it has been common practice to have individual and separate header portions (corresponding to the headers 21 and 22 of the present invention) and to force-fit these header portions on the thin-walled, plunger tubing adapted to receive a solenoid plunger. More specifically, the lower header would be forced on the tubing and then a bobbin wound on a cylindrical tube would be forced over the tubing and finally an upper header would be forced over the upper portion of the tubing. With such a method of fabrication, the tubing was often distorted so that portions of its originally circular bore assumed a noncircular configuration and caused rubbing or frictional contact with the plunger.

In accordance with the preferred embodiment of the present invention, the one-piece bobbin 20 is loosely fitted over the tubing 18 to receive the lower flared portion 35 of the tubing within an annular recess 36 formed in the bottom of the bobbin. The pluger stop 15 having been previously riveted or staked by its end portion 38, FIG. 3, to the base portion or wall 29 of the frame 13, the

flange portion 35 of the tube 18 is positioned over the rounded upper edge 39 of the plunger stop 15. Considerable force is then applied to the upper end 40 of the tube 18 to force the tubing 18 downwardly over the staked plunger stop 15. The outside diameter of the plunger stop and the inner diameter of the metal tubing 18 are so related to one another than a force-fit or interference fit results between the tubing 18 and the plunger stop 15 .at the engaged surfaces. As shown in FIGS. 2 and 3, the lower portion of the plunger stop has a knurled surface 44 over which the plunger tubing 18 is forced to prevent relative twisting between the plunger tubing 18 and the plunger stop 15.

The plunger tubing 18 is longer in length than the distance between the outer surfaces 45 and 46 of the bobbin 20 so that the pressure for forcing the tubing on the plunger stop 15 can be exerted solely on the upper end 40 of the plunger tubing 18 without the application of any force to the upper flange 22 on the bobbin 20. When forcing the tubing 18 downwardly on the plunger stop 15, the projections 30 are aligned with and inserted into the receiving apertures 32 in the base portion 29 of the frame 13. In final position, the flared end 35 of the tubing 18 engages the top surface of the base 29 and the lower header 21 has its lower surface 45 in engagement with the upper surface of the base portion 29, and the projections 30 are disposed in the openings 32.

A top plate or frame portion 50 affording a second base wall opposite the first base wall 29 of the frame 13 has a plurality of projections 51 and slots 52 which are adapted to be engaged with complementary projections 54 and slots 55 respectively, formed on the upper edges of spaced legs 57 and 58 which afford the opposed side walls of the frame.

The top plate 50 has a circular opening 58 therein adapted to receive the upper end portion 40 of the metal tube so that the bottom of the top plate 50 can rest on the upper surface 46 of the upper header 22 when the top plate 50 is inserted on the tube 18.

As best seen in FIGS. 1 and 3, the projections 54 on the tops of the side frame 57 and 58 are clenched or bent over to clamp the top plate 50 tightly against the upper surface 46 of the header 22. As seen in FIG. 3, the upper end 40 of the tube 18 extends into the circular opening 58 and is held against lateral movement by the top plate 50.

The plunger 11 is fitted into the bore 19 of the tubing 18 and the plunger is brought into engagement with the top surface 60 of the plunger stop 15 to complete assembly of the solenoid.

From the foregoing it will be seen that the present invention is fabricated with and employs a novel one-piece bobbin construction having integral headers which fit loosely over the plunger tubing 18 so as not to distort the plunger tubing. At least one of the headers of the bobbin has interlocking parts with the frame of the solenoid to prevent twisting of the bobbin relative to the frame which was heretofore resisted only by frictional engagement between a cylinder supporting the coil and the tubing for the plunger.

Hence, while I have illustrated and described preferred embodiments of the present invention, it is to be understood that these are capable of variation and modification.

I claim:

1. A solenoid comprising a frame having a base wall and a pair of interconnecting side walls extending from and joined at respective ends to said base wall, a cylindrical plunger stop secured to said base wall, a bobbin having a hollow central body and a pair of attached headers at the opposite ends thereof, said bobbin having a coil, an elongated guide tube fitted over said plunger stop, said central body of said bobbin being loosely fitted over and said guide tube with one header thereof disposed adjacent said base wall, a solenoid plunger arranged within said guide tube for sliding movement, and said one header and the base wall having interlocked projections and openings to secure said bobbin against rotation.

2. A solenoid according to claim 1 wherein said plunger stop is fixedly secured to said base wall and is provided with a knurled exterior surface, and said guide tube being force-fitted over said knurled surface.

3. A solenoid according to claim 2 wherein the frame includes a separate second base wall, there being cooperating projections and slots between the side walls and said second base wall clenching the second base wall to said side walls.

4. A solenoid according to claim 3 wherein the other header of the bobbin is adjacent said second base wall, with an end of said guide tube extending beyond said second header and disposed in an opening in said second base wall.

References Cited by the Examiner UNITED STATES PATENTS 2,585,684 2/1952 Roggenstein 29--155.58 X 2,964,837 12/1960 Harris 29-155.58 2,965,954 1-2/1960 Baker 29l55.58 2,987,655 6/ 1961 McCurdy 317158 3,010,055 11/1961 Nicolaus 317191 3,017,547 1/1962 Jencks 317--191 BERNARD A. GI-LHEANY, Primary Examiner.

G. HARRIS, 1a., Assistant Examiner. 

1. A SOLENOID COMPRISING A FRAME HAVING A BASE WALL AND A PAIR OF INTERCONNECTING SIDE WALLS EXTENDING FROM AND JOINED AT RESPECTIVE ENDS TO SAID BASE WALL, A CYLINDRICAL PLUNGER STOP SECURED TO SAID BASE WALL, A BOBBIN HAVING A HOLLOW CENTRAL BODY AND A PAIR OF ATTACHED HEADERS AT THE OPPOSITE ENDS THEREOF, SAID BOBBIN HAVING A COIL, AN ELONGATED GUIDE TUBE FITTED OVER SAID PLUNGER STOP, SAID CENTRAL BODY OF SAID BOBBIN BEING LOOSELY FITTED OVER AND SAID GUIDE TUBE WITH ONE HEADER THEREOF DISPOSED ADJACENT SAID BASE WALL, A SOLENOID PLUNGER ARRANGED WITHIN SAID GUIDE TUBE FOR SLIDING MOVEMENT, AND SAID ONE HEADER AND THE BASE WALL HAVING INTERLOCKED PROJECTIONS AND OPENINGS TO SECURE SAID BOBBIN AGAINST ROTATION. 